//
// Created by Administrator on 2021/6/14.
//

/**
 * Forward declaration of guess API.
 * @param  num   your guess
 * @return 	     -1 if num is lower than the guess number
 *			      1 if num is higher than the guess number
 *               otherwise return 0
 * int guess(int num);
 */

#include <iostream>

using namespace std;

class Solution {
private:
    int target = 0;
public:
    explicit Solution(int target) : target(target) {}  // 构造函数
    int guess(int num) {
        if (num > target) return -1;
        else if (num < target) return 1;
        else return 0;
    }

    int guessNumber(int n) {
        int left = 1, right = n;
        while (left < right) { // 循环直至区间左右端点相同
            int mid = left + (right - left) / 2; // 防止计算时溢出
            if (guess(mid) <= 0) {
                right = mid; // 答案在区间 [left, mid] 中
            } else {
                left = mid + 1; // 答案在区间 [mid+1, right] 中
            }
        }
        // 此时有 left == right，区间缩为一个点，即为答案
        return left;
    }
};

int main() {
    auto sol = Solution(6);
    cout << sol.guessNumber(10) << endl;
    return 0;
}